Colin,
To make a long story short, there were browns too. The makeup of rainbows-to-browns varied from section to section.
From what I saw and caught, the water that was included in the pictures in this report held mostly rainbows. There were a few browns too, but I would guess 80% rainbows or so.
The water that I fished later in the trip held a larger percentage of browns, with some sections that were probably more along the lines of 80% browns.

Cheers,
Tim